Exploring microbial bioactive molecules from Western Ghats,India

Western Ghats are designated as world heritage sites and global biodiversity hotspots. Microbial diversity in this forest area has been largely neglected and is getting attention since the end of the last millennium. In this review, we have studied and organized various microorganisms from Western Ghats and their diversity, important characteristics and potential biotechnological applications. Microorganisms from Western Ghats have been explored individually for potential bioactive molecules. While most of the microorganisms were analyzed for antimicrobial activities, there have been studies on microbial promotion of plant growth. The microbes analyzed included from aquatics, soil, rhizosphere, phyllosphere and even as endophytes. There have been microorganisms which have shown antioxidant and anti-cancerous activities. There are microorganisms capable of degrading plant wastes and also xenobiotics. Microorganisms capable of producing industrially important enzymes have also been reported. The present review explores largely neglected microbial diversity with respect to their ability to produce potential bioactive biomolecules.     

Lactose esters: synthesis and biotechnological applications

Biodegradable nonionic sugar esters-based surfactants have been gaining more and more attention in recent years due to their chemical plasticity that enables the various applications of these molecules. In this review, various synthesis methods and biotechnological implications of lactose esters (LEs) uses are considered. Several chemical and enzymatic approaches are described for the synthesis of LEs, together with their applications, i.e. function in detergents formulation and as additives that not only stabilize food products but also protect food from undesired microbial contamination. Further, this article discusses medical applications of LEs in cancer treatment, especially their uses as biosensors, halogenated anticancer drugs, and photosensitizing agents for photodynamic therapy of cancer and photodynamic inactivation of microorganisms.     

Potential commercial applications of microbial surfactants

Surfactants are surface-active compounds capable of reducing surface and interfacial tension at the interfaces between liquids, solids and gases, thereby allowing them to mix or disperse readily as emulsions in water or other liquids. The enormous market demand for surfactants is currently met by numerous synthetic, mainly petroleum-based, chemical surfactants. These compounds are usually toxic to the environment and non-biodegradable. They may bio-accumulate and their production, processes and by-products can be environmentally hazardous. Tightening environmental regulations and increasing awareness for the need to protect the ecosystem have effectively resulted in an increasing interest in biosurfactants as possible alternatives to chemical surfactants. Biosurfactants are amphiphilic compounds of microbial origin with considerable potential in commercial applications within various industries. They have advantages over their chemical counterparts in biodegradability and effectiveness at extreme temperature or pH and in having lower toxicity. Biosurfactants are beginning to acquire a status as potential performance-effective molecules in various fields. At present biosurfactants are mainly used in studies on enhanced oil recovery and hydrocarbon bioremediation. The solubilization and emulsification of toxic chemicals by biosurfactants have also been reported. Biosurfactants also have potential applications in agriculture, cosmetics, pharmaceuticals, detergents, personal care products, food processing, textile manufacturing, laundry supplies, metal treatment and processing, pulp and paper processing and paint industries. Their uses and potential commercial applications in these fields are reviewed. Received: 29 July 1999 / Received revision: 8 November 1999 / Accepted: 9 November 1999     

Recent applications of biosurfactants as biological and immunological molecules

The interest in microbial biosurfactants has steadily increased during the past decade. In addition to the classical application as emulsifiers of hydrocarbons, they can be used in environmental protection, crude-oil recovery, food-processing industries and in various fields of biomedicine. Biosurfactants have several advantages over chemical surfactants including lower toxicity and higher biodegradability, and are likely to become molecules of the future in areas such as biomedicine and therapeutics. Here, we discuss the role and applications of biosurfactants (mainly glycolipids and lipopeptides) focusing on medicinal and therapeutic perspectives.     

Biosurfactants in agriculture

Agricultural productivity to meet growing demands of human population is a matter of great concern for all countries. Use of green compounds to achieve the sustainable agriculture is the present necessity. This review highlights the enormous use of harsh surfactants in agricultural soil and agrochemical industries. Biosurfactants which are reported to be produced by bacteria, yeasts, and fungi can serve as green surfactants. Biosurfactants are considered to be less toxic and eco-friendly and thus several types of biosurfactants have the potential to be commercially produced for extensive applications in pharmaceutical, cosmetics, and food industries. The biosurfactants synthesized by environmental isolates also has promising role in the agricultural industry. Many rhizosphere and plant associated microbes produce biosurfactant; these biomolecules play vital role in motility, signaling, and biofilm formation, indicating that biosurfactant governs plant–microbe interaction. In agriculture, biosurfactants can be used for plant pathogen elimination and for increasing the bioavailability of nutrient for beneficial plant associated microbes. Biosurfactants can widely be applied for improving the agricultural soil quality by soil remediation. These biomolecules can replace the harsh surfactant presently being used in million dollar pesticide industries. Thus, exploring biosurfactants from environmental isolates for investigating their potential role in plant growth promotion and other related agricultural applications warrants details research. Conventional methods are followed for screening the microbial population for production of biosurfactant. However, molecular methods are fewer in reaching biosurfactants from diverse microbial population and there is need to explore novel biosurfactant from uncultured microbes in soil biosphere by using advanced methodologies like functional metagenomics.     

Advances in microbial biotechnology of bile acids

The recent advances in microbial biotechnology of production of bile acid metabolites helped to identify a number of neutral and acidic steroidal compounds useful as drugs and drug intermediates on a scale which would not have been possible by classical chemical transformations. Microbial transformations viz., hydroxylation, dehydroxylation, reduction of the carbonyl moieties, epimerization, side-chain metabolism, introduction of carbon-carbon double bonds into the steroid nucleus, deconjugation of bile acid conjugates carried out by various microorganisms for production of useful metabolites with special reference to newer techniques including cell immobilization and transposon mutagenesis for selective transformations are reviewed. The different pathways of microbial degradation of bile acids leading to the formation of various products are discussed. A compilation of the metabolites formed by various microorganisms from the bile acids or their conjugates and reported during the period 1979-1992 is also provided.     

Physiological aspects. Part 1 in a series of papers devoted to surfactants in microbiology and biotechnology

Surfactants, both chemical and biological, are amphiphilic compounds which can reduce surface and interfacial tensions by accumulating at the interface of immiscible fluids and increase the solubility, mobility, bioavailability and subsequent biodegradation of hydrophobic or insoluble organic compounds. Investigations on their impacts on microbial activity have generally been limited in scope to the most common and best characterized surfactants. Recently a number of new biosurfactants have been described and accelerated advances in molecular and cellular biology are expected to expand our insights into the diversity of structures and applications of biosurfactants. Biosurfactants play an essential natural role in the swarming motility of microorganisms and participate in cellular physiological processes of signaling and differentiation as well as in biofilm formation. Biosurfactants also exhibit natural physiological roles in increasing bioavailability of hydrophobic molecules and can complex with heavy metals, and some also possess antimicrobial activity. Chemical- and indeed bio-surfactants may also be added exogenously to microbial systems to influence behaviour and/or activity, mimicking the latter effects of biosurfactants. They have been exploited in this way, for example as antimicrobial agents in disease control and to improve degradation of chemical contaminants. Chemical surfactants can interact with microbial proteins and can be manipulated to modify enzyme conformation in a manner that alters enzyme activity, stability and/or specificity. Both chemical- and bio-surfactants are potentially toxic to specific microbes and may be exploited as antimicrobial agents against plant, animal and human microbial pathogens. Because of the widespread use of chemical surfactants, their potential impacts on microbial communities in the environment are receiving considerable attention.     

Screening concepts,characterization and structural analysis of microbial-derived bioactive lipopeptides: a review

Lipopeptide biosurfactants are surface active biomolecules that are produced by a variety of microorganisms. Microbial lipopeptides have gained the interest of microbiologists, chemists and biochemists for their high biodiversity as well as efficient action, low toxicity and good biodegradability in comparison to synthetic counterparts. In this report, we review methods for the production, isolation and screening, purification and structural characterization of microbial lipopeptides. Several techniques are currently available for each step, and we describe the most commonly utilized and recently developed techniques in this review. Investigations on lipopeptide biosurfactants in natural products require efficient isolation techniques for the characterization and evaluation of chemical and biological properties. A combination of chromatographic and spectroscopic techniques offer opportunities for a better characterization of lipopeptide structures, which in turn can lead to the application of lipopeptides in food, pharmaceutical, cosmetics, agricultural and bioremediation industries.     

Review Degradation of microbial polyesters

Microbial polyhydroxyalkanoates (PHAs), one of the largest groups of thermoplastic polyesters are receiving much attention as biodegradable substitutes for non-degradable plastics. Poly(D-3-hydroxybutyrate) (PHB) is the most ubiquitous and most intensively studied PHA. Microorganisms degrading these polyesters are widely distributed in various environments. Although various PHB-degrading microorganisms and PHB depolymerases have been studied and characterized, there are still many groups of microorganisms and enzymes with varying properties awaiting various applications. Distributions of PHB-degrading microorganisms, factors affecting the biodegradability of PHB, and microbial and enzymatic degradation of PHB are discussed in this review. We also propose an application of a new isolated, thermophilic PHB-degrading microorganism, Streptomyces strain MG, for producing pure monomers of PHA and useful chemicals, including D-3-hydroxycarboxylic acids such as D-3-hydroxybutyric acid, by enzymatic degradation of PHB.     

Rapid and robust MALDI-TOF MS techniques for microbial identification: a brief overview of their diverse applications

in mass spectrometry have enabled the investigation of various biological systems by directly analyzing diverse sets of biomolecules (i.e., proteins, lipids, and carbohydrates), thus making a significant impact on the life sciences field. Over the past decade, matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF MS) has been widely utilized as a rapid and reliable method for the identification of microorganisms. MALDI-TOF MS has come into widespread use despite its relatively low resolving power (full width at half maximum, FWHM: < 5,000) and its incompatibility with tandem MS analysis, features with which other high-resolution mass spectrometers are equipped. Microbial identification is achieved by searching databases containing mass spectra of peptides and proteins extracted from microorganisms of interest, using scoring algorithms to match analyzed spectra with reference spectra. In this paper, we give a brief overview of the diverse applications of rapid and robust MALDI-TOF MS-based techniques for microbial identification in a variety of fields, such as clinical diagnosis and environmental and food monitoring. We also describe the fundamental principles of MALDI-TOF MS. The general specifications of the two major MS-based microbial identification systems available in the global market (BioTyper® and VITEK® MS Plus) and the distribution of these instruments in Republic of Korea are also discussed. The current review provides an understanding of this emerging microbial identification and classification technology and will help bacteriologists and cell biologists take advantage of this powerful technique.     

促进电活性微生物产电呼吸能力的方法研究进展

产电呼吸是指电活性微生物(electroactive microorganisms,EAMs)以胞外固体电极作为电子受体的一种呼吸形式,在可再生能源利用和环境修复方面具有广阔的应用前景。能否进一步提高EAMs的产电呼吸能力是相关技术能否从实验室走向实际应用的核心,而提高产电呼吸能力的关键是加强EAMs与胞外固体电极间的电子传递能力。目前总结如何促进EAMs产电呼吸能力的综述文献极少。因此,本文从投加化学试剂、施加物理作用及改造生物基因3个方面总结了现有的促进EAMs产电呼吸能力的方法,介绍了每种方法的优势与缺陷,重点阐述了每种手段的作用机理及促进效果,并从实际应用和机理研究的角度展望了今后的研究方向。     

Effects of combining microbial and chemical insecticides on mortality of the Pecan Weevil (Coleoptera: Curculionidae)

The pecan weevil, Curculio caryae (Horn), is a key pest of pecan [Carya illinoinensis (Wangenh.) K. Koch]. Current control recommendations are based on chemical insecticide applications. Microbial control agents such as the entomopathogenic nematode, Steinernema carpocapsae (Weiser) and the fungus Beauveria bassiana (Balsamo) Vuillemin occur naturally in southeastern U.S. pecan orchards and have shown promise as alternative control agents for C. caryjae. Conceivably, the chemical and microbial agents occur simultaneously within pecan orchards or might be applied concurrently. The objective of this study was to determine the interactions between two chemical insecticides that are used in commercial C. caryae control (i.e., carbaryl and cypermethrin applied below field rates) and the microbial agents B. bassiana and S. carpocapsae. In laboratory experiments, pecan weevil larval or adult mortality was assessed after application of microbial or chemical treatments applied singly or in combination (microbial + chemical agent). The nature of interactions (antagonism, additivity, or synergy) in terms of weevil mortality was evaluated over 9 d (larvae) or 5 d (adults). Results for B. bassiana indicated synergistic activity with carbaryl and antagonism with cypermethrin in C. caryae larvae and adults. For S. carpocapsae, synergy was detected with both chemicals in C. caryae larvae, but only additive effects were detected in adult weevils. Our results indicate that the chemical-microbial combinations tested are compatible with the exception of B. bassiana and cypermethrin. In addition, combinations that exhibited synergistic interactions may provide enhanced C. caryae control in commercial field applications; thus, their potential merits further exploration.     

Extremophiles as a source for novel enzymes

Microbial life does not seem to be limited to specific environments. During the past few decades it has become clear that microbial communities can be found in the most diverse conditions, including extremes of temperature, pressure, salinity and pH. These microorganisms, called extremophiles, produce biocatalysts that are functional under extreme conditions. Consequently, the unique properties of these biocatalysts have resulted in several novel applications of enzymes in industrial processes. At present, only a minor fraction of the microorganisms on Earth have been exploited. Novel developments in the cultivation and production of extremophiles, but also developments related to the cloning and expression of their genes in heterologous hosts, will increase the number of enzyme-driven transformations in chemical, food, pharmaceutical and other industrial applications.     

海洋微型生物储碳过程与机制概论

在全球气候环境演变的背景下,认识海洋微型生物对碳循环的贡献,需要了解其过程和机制.最近提出的“微型生物碳泵”理论阐释了海洋储碳的一个新机制:微型生物活动把溶解有机碳从活性向惰性转化,从而构成了海洋储碳.这个过程当中,自养与异养细菌、病毒、原生动物等具有不同生理特性微型生物类群扮演着不同的生态角色,本文将围绕微型生物碳泵主线分别论述之.     

表面活性剂影响微生物降解多环芳烃的研究进展

多环芳烃(Polycyclic Aromatic Hydrocarbons,PAHs)的强疏水性是阻止其在土壤和水环境中微生物降解的主要因素.表面活性剂由于能够提高PAHs的表观溶解度而在PAHs的微生物降解中得到了广泛研究.截至目前,有关化学或生物表面活性剂促进PAHs的微生物降解已有大量报道,然而也有学者发现了表面...     

Surfactants in microbiology and biotechnology: Part 2. Application aspects

Surfactants are amphiphilic compounds which can reduce surface and interfacial tensions by accumulating at the interface of immiscible fluids and increase the solubility, mobility, bioavailability and subsequent biodegradation of hydrophobic or insoluble organic compounds. Chemically synthesized surfactants are commonly used in the petroleum, food and pharmaceutical industries as emulsifiers and wetting agents. Biosurfactants produced by some microorganisms are becoming important biotechnology products for industrial and medical applications due to their specific modes of action, low toxicity, relative ease of preparation and widespread applicability. They can be used as emulsifiers, de-emulsifiers, wetting and foaming agents, functional food ingredients and as detergents in petroleum, petrochemicals, environmental management, agrochemicals, foods and beverages, cosmetics and pharmaceuticals, and in the mining and metallurgical industries. Addition of a surfactant of chemical or biological origin accelerates or sometimes inhibits the bioremediation of pollutants. Surfactants also play an important role in enhanced oil recovery by increasing the apparent solubility of petroleum components and effectively reducing the interfacial tensions of oil and water in situ. However, the effects of surfactants on bioremediation cannot be predicted in the absence of empirical evidence because surfactants sometimes stimulate bioremediation and sometimes inhibit it. For medical applications, biosurfactants are useful as antimicrobial agents and immunomodulatory molecules. Beneficial applications of chemical surfactants and biosurfactants in various industries are discussed in this review.     

Microbial cellulose as a specialty chemical

Microbial polysaccharides are extensively used commercially as gelling or suspending agents, as protective colloids or as thickening agents. Until recently, microbial cellulose producing systems such as Acetobacter xylinum, had been used largely as model systems for the study of cellulose biosynthesis. Current advances in molecular biology and biochemical engineering promise to usher microbial cellulose into the specialty chemical market. This review will highlight some of the recent progress made in our understanding of microbial cellulose biochemistry and biosynthesis, describe some of its inherent virtues and identify current unique applications of this versatile biopolymer.     

微生物性状揭示物种分布格局、群落构建机制和生态系统功能

微生物性状是指与其存活、生长和繁殖紧密相关的一系列核心属性,这些属性能够反映微生物对环境变化的响应,进而影响微生物的物种分布格局、群落构建机制以及相应的生态系统功能。越来越多的研究表明,相比于微生物分类学信息,微生物性状可以在种群、群落和生态系统尺度等视角扩展我们对微生物生态过程的理解,并提供生态模式的机理性解释。本文回顾微生物性状研究的发展历程,总结近年来基于微生物性状研究的前沿科学问题,比如微生物性状的分类和测定方法、基于性状的功能多样性定义及应用、性状与物种分布格局和群落构建机制的关系、性状对生物多样性和生态系统功能的影响以及对环境变化的响应等。尽管微生物性状研究已经延伸到生态学领域的各个方面,有力推动着各个前沿科学问题的研究发展,但是仍然面临很多机遇与挑战。因此,本文也从研究方法和研究方向等方面对未来基于微生物性状的研究提出了展望。     

Engineering microbial consortia: a new frontier in synthetic biology

Microbial consortia are ubiquitous in nature and are implicated in processes of great importance to humans, from environmental remediation and wastewater treatment to assistance in food digestion. Synthetic biologists are honing their ability to program the behavior of individual microbial populations, forcing the microbes to focus on specific applications, such as the production of drugs and fuels. Given that microbial consortia can perform even more complicated tasks and endure more changeable environments than monocultures can, they represent an important new frontier for synthetic biology. Here, we review recent efforts to engineer synthetic microbial consortia, and we suggest future applications.     

绿弯菌的研究现状及展望

绿弯菌是一个深度分支的门级别细菌类群,广泛分布于生物圈各种生境。现已生效发表的绿弯菌构成9个纲,但仅包含56个种;基于分子生态学的研究结果表明尚有大量绿弯菌类群仍是未培养状态。绿弯菌形态多样,营养方式和代谢途径十分丰富,参与了C、N、S等一系列重要生源元素的生物地球化学循环过程。研究该类群不仅有助于认识环境中微生物的多样性及其代谢特征,从而更好的理解微生物参与的生态学过程,还有助于揭示微生物对环境的适应及其进化。本文主要综述了绿弯菌的发现历史、营养、代谢及其在元素循环中的作用,并总结了其分离培养和潜在应用价值,最后展望了未来的研究方向,旨在为深入探究绿弯菌的进化、培养和驱动地球化学元素循环等研究提供参考。